Hydrophilic surfaces and in particular surfaces which have a hydrophilic coating are used especially for microfluidic elements (i.e., microstructures through which a liquid should flow). Such microfluidic elements are used especially in analytical systems for body fluids, for example in blood sugar measuring instruments which enable diabetics to self-monitor their blood sugar level. In this case, the microfluidic test element can comprise a lancing member which is provided with or connected to a microchannel for the capillary transport of the body fluid. Examples of such microneedles or microsamplers are disclosed in WO 2006/021361, and are usually provided as disposable parts.
The microchannel and, where appropriate, the lancing member should be made out of a biocompatible material which can be mechanically stressed and sterilized in a simple manner. Surgical steel is particularly suitable for this, but its hydrophilicity is too low to allow a capillary transport of aqueous body fluids through the microchannel. For this reason, such microfluidic elements may be provided with a hydrophilic surface coating. The surface coating should in addition be biocompatible and sterilizable and should allow the microchannel to be filled within a very short period.
Finally, an adequate long-term stability of the surface coating is desirable. Hydrophilic coatings usually have high-energy surfaces. This is thermodynamically unfavorable because the surface tries to reduce its high energy by reducing the hydrophilicity. This occurs, for example, by the adsorption of apolar gas molecules. Packaging materials and in particular polymeric packaging materials can, however, contain a considerable proportion of apolar gases which escape over time from the packaging material. In addition, air is always enclosed in the packaging. It is therefore desirable to reduce the proportion of undesired gases in the packaging.
Desiccants such as activated carbon, silica gels and molecular sieves are generally used to adsorb undesired gases in packaging (cf. EP 0 951 939 A2). However, the use of these materials can be problematic for objects with a hydrophilic surface coating for medical purposes such as microneedles or lancets. In addition, it is unclear to what extent the particularly undesired apolar gases are reduced.
Hence, the present disclosure describes a package for an object having a hydrophilic surface. The package maintains the hydrophilicity of the surface during a storage period and is simple to produce and to use. In particular, the package facilitates the use of disposable microfluidic test elements in analytical systems.
In one embodiment, the package includes at least one loose cover and/or at least one adsorbing surface, the affinity of which for apolar gases is equal to or greater than that of the hydrophilic surface of the object.
It has surprisingly turned out that even a loose cover (i.e., one which is not glued or otherwise attached such as a cover plate or cover fleece) is sufficient as a screen to impede the apolar gases from gaining access to the hydrophilic surface of the packaged object to such an extent that the hydrophilicity of the surface remains reliably stable even over long periods. One only has to take care that the loose cover does not itself release any apolar gases.
The same result is achieved when an additional adsorbing surface is present within the package which itself adsorbs apolar gases at least equally as well as the hydrophilic surface of the packaged object.
The package according to the present disclosure can reduce the adsorption of apolar gases onto the hydrophilic surface in a particularly simple and effective manner such that the package is well-suited for medical mass products without excessively increasing the costs.
According to another embodiment of the present disclosure, the at least one adsorbing surface is designed in the form of at least one adsorber element having an adsorbing surface that is packaged with the object. Such an adsorber element, for example in the form of a small plate or fleece, can be automatically added in a simple manner when the object having a hydrophilic surface is packaged.
The at least one adsorber element can, in particular, be in the form of a cover for the hydrophilic surface itself such that the access of apolar gases to the hydrophilic surface is additionally impeded.
In another embodiment, the at least one adsorber element can have an adsorber layer in the form of a hydrophilic coating. In this case the hydrophilicity (i.e., the surface energy) of the adsorber layer should be equal to or greater than the hydrophilicity (i.e., the surface energy) of the surface of the packaged object in order to ensure an effective adsorption of the apolar gases to the adsorber layer. The hydrophilic coating can consist of the same material as the hydrophilic surface of the packaged object so that the adsorber layer is automatically biocompatible and sterilizable.
Another embodiment of the adsorber layer according to the disclosure is a hydrophilic coating on at least a portion of the inside of the package with a hydrophilicity or surface energy equal to or greater than the hydrophilicity or surface energy of the surface of the packaged object to ensure an effective adsorption of the apolar gases to the adsorber layer. Also in this case the hydrophilic coating can consist of the same material as the hydrophilic surface coating of the packaged object so that the adsorber layer is automatically biocompatible and sterilizable.
Numerous materials are generally known for hydrophilic coatings such as, for example, lecithin or dextran sulfate. Particularly suitable materials which can be present in a hydrophilic coating or of which a hydrophilic coating can consist, are polyacrylic acids and polyacrylates. These are biocompatible and sterilizable and therefore particularly well-suited, especially for coating packaging in the medical field or for microfluidic systems having hydrophilic surface coatings such as, for example, microneedles for portable blood sugar measuring instruments.
The present disclosure also concerns the unit including a package with contents (i.e., a package containing a microfluidic element having a hydrophilic surface for taking up a body fluid and at least one loose cover which covers the hydrophilic surface and/or at least one adsorbing surface, the affinity of which for apolar gases is equal to or greater than that of the hydrophilic surface).
The teachings of the present disclosure will be better understood upon reference to the following description on the basis of the embodiment example shown schematically in the drawings.